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RETIREMENT AND POSTRETIREMENT PLANS - Dime KSOP Plan - BMP and Outside Director Retirement Plan (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2022 | Mar. 31, 2021
BMP and Outside Director Retirement Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Termination Age of Board Members | 75 years |
Curtailment loss |  | $ 1.5
Outside Director Retirement Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Obligation | $ 2.8 |
Board Member Retirement Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Obligation | $ 6.2 |

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- Definition Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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